Elastic properties of monolithic porous blocks of compressed expanded graphite related to their specific surface area and pore diameter

Highly porous monolithic blocks of compressed expanded graphite (CEG) with various apparent densities ranging from 0.026 to 0.276 g cm−3, produced of initial expanded graphite of an apparent density of 4 g l−1, were characterized using a gas helium pycnometer, a mercury porosimetry and physical adsorption of N2 gas at 77 K. The dynamic elastic module of CEG cubes were determined by means of measurements of the velocity of the longitudinal ultrasonic wave (frequency of 100 kHz) propagated along three mutually orthogonal directions: parallel and perpendicular to the bedding plane (or the uniaxial compression direction). CEG was found to be characterized by macropores and mesopores of various diameters. The most probable sizes of pores are 10, 2.4, and 0.9 μm, 4 and 2.5 nm. The elastic properties were related to the porous structure of CEG—represented by the volume of open and closed pores, specific surface area SBET and pore diameter.